The present invention relates to a combined support and guide for the mandrel of a continuous rolling mill of the type having a restrained mandrel.
In a mill of the aforesaid type, a tubular intermediate forging to be rolled is fitted on to a mandrel for passage through the successive rolling stands. More precisely, a straight mandrel is inserted coaxially into the intermediate forging, which is supported coaxially with the rolling axis upstream of the first stand of the mill, the forging being fitted to the mandrel with a predetermined shrinkage. Subsequently, the mandrel and intermediate forging are moved as a unit through the successive stands of the mill, still on the rolling axis, with a controlled velocity. This unit is stopped when the tip of the mandrel corresponds with the mouth of the cylinders of the last rolling stand, which effects the last rolling operation on the intermediate forging and allows the simultaneous removal of the finished tube from the mandrel. The mandrel is then returned to its original position for insertion into a further intermediate forging to be rolled in the mill.
In order to ensure the proper operation of such a rolling mill to give good results in the finished product, the outer surface of the mandrel is accurately worked mechanically, and is covered with a layer of suitable lubricant. During the movements of the mandrel through the rolling stands, of the known mills, however, it may, and in fact, frequently does come into contact with, and even bangs against, the rolling cylinders, with consequent removal of the lubricating layer and damage to its outer surface. This is due to the fact that the mandrels are not always perfectly straight, the stands are not always perfectly aligned on the rolling axis, and the velocity of rectilinear movement of the mandrel through the stands is relatively high.
Such damage to the mandrel may result in seizure of a tube being rolled on the mandrel, this problem being accentuated when the aperture of passage through the stands is very small, as is required for the rolling of tubes of small thickness.
The object of the present invention is to provide a combined support and guide for a mandrel during its traverse through the rolling mill, which supports and guides the mandrel to reduce its contact with the rolling cylinders.